Telephone-exchange system



H. W. ULRICH.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JAN-4,1918.

Patented Jan. 4, 1921.

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HORACE VI. ULRICH, 015 EAST ORANGE, NEW JERSEY, ASSIG-NQR TO WESTERN ELEC- TRIO COMPANY, INCGB'EOBATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Jan. 4, 1921.

Application filed January 4, 1918. Serial No. 210,238.

To all w from it may concern:

Be it known that 1, Homer VJ. ULRICH, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone exchange systems, and more particularly to such systems which employ automatic ringing for signaling purposes and which are provided with trunk lines extending to the chief operators desks, private branch 6X- changes, information desks and like positions.

The object of this invention is to provide a system of this character in which the source of ringing current is automatically disconnected from the trunk line before the answering operators receiver is operatively associated with the line, thereby to eliminate the disagreeable clicks which are usually present when an operator answers a call over a line to which is connected a trunk or cord circuit equipped for automatic ringing.

In accordance with this invention, when an operator answers a call over a line to which is connected an automatic ringing cord circuit, by actuating a switching device in the nature of a listening key, ringing current is thereby automatically disconnected and the operators telephone set is connected with the line, but the receiver thereof is not operatively associated with theline until after ringing current has been disconnected from the trunk line.

This invention is illustrated in the accompanying drawing in which all apparatus is shown in its normal and unactuated position.

There is shown in the drawing a telephone exchange system containing one embodiment of this invention and comprising a cord circuit A, located at one section C of a switchboard, and a trunk circuit B ex tending from this section C to a desk operators position D, at which there is a signaling device, a listening key and an opera tors telephone set. It is believed that this invention will be fully understood from a description of the operation of the system shown in the drawing, and it will be so described.

The operator at section C, desiring to signal the desk operator D, inserts plug 5 of the cord circuit A into a jack 6, whereupon lamp 7 will be lighted and relay 8 operated- The operation of relay 8 causes the energization of a ringing relay 9 over a circuit from battery through resistance 10, Winding of relay 9, normal contact of relay 11, contact 01 tripping relay 12, and the closed contact of relay 8 to ground. The energi- Zation of ringing relay 9 connects a source of ringing current 15 t0 the trunk circuit 13, causing the operation of relay 16 over a circuit from the source of ringing current 15 through the winding of tripping relay 12, lower alternate contact of ringing relay 9, ring contacts of the plug 5 and the jack 6, condenser 17, right-hand winding of relay 16, tip contacts of the jack 6 and the plug- 5, and the upper alternate contact of ringing relay 9 to ground. The operating or energizing winding of-relay 16 is of high resistance so that the tripping relay 12 is not actuated when in circuit with this winding of relay 16. Upon the energization of relay 16, it is locked up over a circuit from battery through the left-hand winding and contact thereof and the normally closed contact of listening key 18 to ground. The lamp 19 is lighted upon the energization of relay 16 to furnish a signal to the desk operator, and remains lighted until the desk operator actuates the listening key 18. Ringing current also remains connected to the trunk circuit until the actuation of the listening key 18.

The desk operator, upon observing the lighted condition of lamp 19, actuates listening key 18, which opens the locking circuit of relay l6 and the circuit of the lamp 19, thereby releasing the relay and extinguishing the lamp. The closure of contacts 25 and 26 of the listening key 18 connects a relay 27 and an impedance coil 28 in bridge of the trunk circuit. This relay 27 is thereupon operated by .ringing current and, in operating, short-circuits the left-hand winding of the impedance coil 28, leaving the right-hand winding thereof bridged across the trunk circuit. This right-hand winding is of low impedance so that, when included in circuit with the source of ringing current 15, the tripping relay 12 operates.

Relay 12, in operating, opens its contact, removing a short circuit from and permitting relay 11 to operate. Relay 11 is thereupon locked up over a circuit from battery through resistance 10, alternate contact and winding of relay 11 and the contact of relay 8 to ground. The operation of relay 11 also establishes a short circuit for the ringing relay 9, which thereupon releases, removing ringing current from the trunk circuit. The closure of its normal contacts, upon the release of the ringing relay 9, causes the operation of supervisory relay 2 1 Over a circuit from battery through repeating coil winding 23, winding of supervisory relay 2 1,lower normal contact of ringing relay 9, ring contacts of the plug 5 and the jack 6, contact 26 of listening key 18, both windings of impedance coil 28 (relay 27 having released when the ringing current was d sconnected), contact 25 of listening key 18, tip contacts of the jack 6 and the plug 5, the upper normal contact of ringing re lay 9 and repeating coil winding 22 to ground. The operation of the supervisory relay 24 connects the resistance coil 10 in parallel with the lamp 7, which is thereby extinguished, indicating to the operator at section C that the desk operator D has answered.

The actuation of listening key 18 also closes its contacts 29 and 30. The closure of contact 29 causes the operation of a slow release relay 31 over a circuit from battery through the normal contact of relay 32, winding of relay 31 and contact 29 of listening key 18 to ground. Relay 31, in operating, causes theoperation of relay 32 over a circuit from battery through the alternate contact of relay 31, winding 01? relay 32, impedance coil 33, the primary winding of induction coil 34, transmitter 35 and contact 29 of listening key 18 to ground. Current is furnished over this path for the operation of the transmitter 35. Relay 32, in operating, first opens the circuit of slow release relay 31 and then establishes a locking circuit for itself through its alternate contact. Upon the complete release of the slow-to-release relay 31, relay 36 is energized over a circuit from battery through the alternate contact of relay 32, normal contact 01' relay 31, winding of relay 36,

impedance coil 33, primary Winding of the induction coil 34, transmitter 35 and contact 29 of listening key 18. The energizationof relay 36 opens its contact, thereby removing a short circuit from the receiver 37 of the operators telephone set. The operators telephone set is connected to the trunk circuit by the closure of contacts 25, 26 and 30 when the listening key 18 is actuated, but the receiver 37 of the operators telephone set is not operatively associated with the trunk circuit until after the fol lowing operations take place in the sequence named: (1) energization of relay 31, (2)

the energization of relay 32, the release 01" relay 31 and (4) the energization of relay 36. This sequence of operation insures that the short circuit will not be removed from the receiver until after ringing current V has been disconnected from the trunk circuit.

At the conclusion ofthe conversation, the desk operator D restores the listening key 18 to normal, whereupon relays 32 and 36 are restored to normal condition. Supervisory relay 24; also releases, thereby perniitting the lamp 7 to be lighted, whereupon the operator at position C withdraws the plug 5 from the jack 6, restoring all apparatus of the cord circuit A to normal condition. 7

What is claimed is:

1. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board having a re ceiver, normally effective means for disabling said receiver, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and means responsive to the actuation of the switch for rendering the disabling means ineITective after ringing current has been removed from the trunk circuit.

2. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board having a receiver, normally effective means for disabling said receiver, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and a relay responsive to the actuation of the switch for rendering the disabling means ineffective after ringing current has been removed from the trunk circuit.

3. A telephone exchange system compris ing a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the ,other board, an operators telephone set at said other board having a receiver, means for normally short-circuiting said receiver, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and means responsive to the actuation of the switch for removingthe short circuit:

other board, an operators telephone set at said other board having a recelver, means for normally short-ci rcuiting said receiver,

a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and a relay responsive to the actuation of the switch for removing the short circuit from the receiver after ringing current has been removed from the trunk circuit.

5. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators. telephone set at said other board having a receiver, means for normally short-circuiting said receiver, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit,

a slow-to-release relay energized upon the I actuation of the switch, a second relay actuated upon the energization of the slowto-release relay, and a third relay responsive to the actuation of the second relay upon the deenergization of the slow-to-release relay for removing the short circuit from the receiver;'

6. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and means responsive to the actuation of the switch for causing the operative association of the receiver or the operators telephone set with the trunk circuit after ringing current, is disconnected therefrom.

7. A telephone exchange system comprising a trunk circuit extending phone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from one telefrom tllBtlllIllK' circuit, and a relay responsive to :theactuation of the switch for causing the'operative association ofthe receiver or" the operators telephone set with the trunk circuit after ringing current is disconnected therefrom.

8. A telephone exchange system comprising a trunh'circuit extending from one telephone switchboard to a second switchboard, means at oneof the boards for applying ringing current over the'trunk circuit to the other board, an operators telephone set at said other board, a switch thereat actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, a slow-to-release relay energized upon the actuation of the switch, a second relay actuated upon the energization of the slow-to-release relay, and a third relay responsive to the actuation of the second relay upon the deenergization of the slowto-release relay for causing the operative association of the receiver of the operators telephone set with the trunk circuit after ringing current is disconnected therefrom.

9. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board comprising a transmitter and a receiver, a source of current, a switch at said other board actuated by the operator for connecting the operators telephone set to the trunk circuit and for disconnecting the ringing current from the trunk circuit, and means responsive to the actuation of the switch for connecting the source of current in circuit with the transmitter and for causing the operative association of the-receiver with the trunk circuit after the ringing current is disconnected therefrom.

10. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard,'means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set at said other board comprising a transmitter and receiver, a switch thereat actuated by the operator for disconnecting the ringing current from the trunk circuit, a source of current connected in circuit with the transmitter upon the actuation of the switch, and a relay responsive to the actuation of the switch for causing the operative association of the receiver with the trunk circuit after ringing current is disconnected therefrom.

11. A telephone exchange system comprising a trunk circuit extending from one telephone switchboard to a second switchboard, means at one of the boards for applying ringing current over the trunk circuit to the other board, an operators telephone set atsa'id other board comprising a transmitter r and receiver, a switch thereat actuated by the operator for disconnecting the ringing current from. the trunk circuit, a slow-t0- release relay energized by the actuation of the switch, a second relay'actuated upon the energization of the slow-to-release relay, a source of current connected in circuit with the transmitter by the actuation of the secon'd relay, and. a third relay responsive to the actuation of the second relay upon the denergization of the sloW-to-release relay for causing the operative association of the receiver With the trunk circuit after ringing current is disconnected therefrom.

In Witness whereof, I hereunto subscribe my7name this 29th day of December, A. D. 191 v HORACE W. ULRICH. 

